Abstract
The need for protein of Bombus terrestris workers was investigated by examining
the effect of pollen availability on their longevity. Workers were kept under
three conditions: provided with sugar solution only, with sugar solution and pollen
ad libitum, and with sugar solution and pollen for 6 hours. Worker survival curves
differed significantly among all conditions. Pollen deprivation led to a strong
decline in survivorship whereas access to pollen for 6 hours only had a small
and transient positive effect. This indicates that adult bumblebees have an ongoing
need for protein food throughout their lives and confirms the observation that workers
that eat pollen without subsequently feeding larvae do so for their own needs. There was
no correlation between worker size and longevity, indicating that the reported higher
mortality of foragers is not due to their bigger size. Our results show that,
when environmental variables are excluded, workers die of senescence after
about two months.